This also bugs me when people say "Oh, that person's given this talk at that conference before". Preparing a good talk is a lot of work, and after that's put in why should you not be allowed to give that talk more than one time?
Also only very few people watch conference videos. Giving the same talk a dozen times, by the 10th time maybe a handful of people in an audience of hundreds will have seen the talk before. I'm honestly surprised conferences still record the talks because I'm fairly certain it's not worth the money for them. (there are outliers to this when somebody gives the most amazing talk ever that gets watch millions of times, but how often does that happen?)
I'd much rather conferences invest money into a better experience for the attendees and speakers.